<?php
class Captcha
{
    var $width='80';
    var $num='4';
    var $height='24';
    var $name='randcode';
    public function __construct($conf="")
    {
        if($conf!="")
        {
            foreach($conf as $key=>$value)
            {
                $this->$key=$value;
            }
        }
    }

    function show()
    {
        Header("Content-type: image/gif");
        /*
        * 初始化
        */
        $border = 0; //是否要边框 1要:0不要
        $how = $this->num; //验证码位数
        $w = $this->width; //图片宽度
        $h = $this->height; //图片高度
        $fontsize = 5; //字体大小
        $alpha = "abcdefghijkmnopqrstuvwxyz"; //验证码内容1:字母
        $number = "023456789"; //验证码内容2:数字
        $randcode = ""; //验证码字符串初始化
        srand((double)microtime()*1000000); //初始化随机数种子

        $im = ImageCreate($w, $h); //创建验证图片

        /*
        * 绘制基本框架
        */
        $bgcolor = ImageColorAllocate($im, 255, 255, 255); //设置背景颜色
        ImageFill($im, 0, 0, $bgcolor); //填充背景色
        if($border)
        {
            $black = ImageColorAllocate($im, 0, 0, 0); //设置边框颜色
            ImageRectangle($im, 0, 0, $w-1, $h-1, $black);//绘制边框
        }

        /*
        * 逐位产生随机字符
        */
        for($i=0; $i<$how; $i++)
        {
            $alpha_or_number = mt_rand(0, 1); //字母还是数字
            $str = $alpha_or_number ? $alpha : $number;
            $which = mt_rand(0, strlen($str)-1); //取哪个字符
            $code = substr($str, $which, 1); //取字符
            $j = !$i ? 4 : $j+15; //绘字符位置
            $color3 = ImageColorAllocate($im, mt_rand(0,100), mt_rand(0,100), mt_rand(0,100)); //字符随即颜色
            ImageChar($im, $fontsize, $j, 3, $code, $color3); //绘字符
            $randcode .= $code; //逐位加入验证码字符串
        }

        /*
        * 添加干扰
        */
        for($i=0; $i<5; $i++)//绘背景干扰线
        {
            $color1 = ImageColorAllocate($im, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255)); //干扰线颜色
            ImageArc($im, mt_rand(-5,$w), mt_rand(-5,$h), mt_rand(20,300), mt_rand(20,200), 55, 44, $color1); //干扰线
        }
        for($i=0; $i<$how*15; $i++)//绘背景干扰点
        {
            $color2 = ImageColorAllocate($im, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255)); //干扰点颜色
            ImageSetPixel($im, mt_rand(0,$w), mt_rand(0,$h), $color2); //干扰点
        }

        //把验证码字符串写入session

        //$this->session->set_userdata(array($this->name=>$randcode));

        $_SESSION[$this->name]=$randcode;
        /*绘图结束*/
        Imagegif($im);
        ImageDestroy($im);
        /*绘图结束*/
    }
}
?>